1. Field of the Invention
The present invention relates to a fan device. More specifically, it relates to an improvement of a fan device for an engine cooling system of industrial application including construction equipment such as an excavator and other vehicles or a fan device for various industrial cooling system.
2. Description of Related Art
Conventionally, in an engine-cooling system of vehicle etc., an engine is cooled by a coolant circulating between the engine and a radiator. The coolant is cooled by a cooling air sucked in or pushed by a fan adjacent to the radiator.
FIG. 13 shows a conventional fan 92 disposed between a radiator 91 and an engine (not shown). The fan 92 has an approximately cylindrical rotation locus around a rotation axis (not shown) drawn by respective edges during rotation. An outer circumference of the cylindrical rotation locus often traces a straight section 94 parallel to the axis line of the rotation axis, irrespective of difference in profile of a fan shroud 93 opposing an outer circumference of the fan 92.
For improving performance of the fan, flow rate of the fan has to be increased without changing size and rotation frequency of the fan and noise such as jet noise caused by swirl has to be reduced.
However, since a configuration of proximal end of the fan 92 is the straight section 94 and the configuration of the fan shroud 93 is bell-mouth shaped at an inlet side and an outlet side, a tip clearance between the proximal end of the fan 92 and the fan shroud 93 is enlarged at the inlet side and the outlet side, so that large number of swirl is generated, thus preventing smooth flow of cooling air.
In other words, increase in flow rate of the cooling air and noise reduction can be limited according to a combination of the fan and the fan shroud having the configuration shown in FIG. 13, and solution thereof has been desired.
An object of the present invention is to provide a fan device capable of securely increasing flow rate and reducing noise. In the present invention, the above object is achieved by modifying configuration of proximal end of a fan.
Specifically, a fan device according to the present invention has a fan, a rotation locus of an outer configuration of a proximal end of the fan being center-dented where a middle section along a direction parallel to an axis line of a rotation axis of the fan is dented relative to both sides thereof on a substantially entire area parallel to the axis line of the rotation axis of the fan.
In the present invention, since the rotation locus of the proximal end of the fan is center-dented to conform to the flow of the cooling air, the cooling air can be smoothly sucked in along the configuration. Further, since natural flow toward radially outward flow of the cooling air can be guided by an arcuate section on an outlet side, thus smoothly discharging the cooling air. Therefore, the flow of the cooling air can be made smooth entirely from upstream to downstream, thus increasing flow rate and reducing noise.
Incidentally, in the present invention, the term xe2x80x9ccenter-dented where a middle section along a direction parallel to an axis line of a rotation axis of the fan is dented relative to both sides thereof on a substantially entire area parallel to the axis line of the rotation axis of the fanxe2x80x9d means a configuration of the approximately cylindrical rotation locus, where the middle section in the rotation axis direction of the rotation locus has relatively small diameter and both sides sandwiching the middle section has relatively great diameter.
In such xe2x80x9ccenter-dented configurationxe2x80x9d, the term xe2x80x9con a substantially entire areaxe2x80x9d is used for a concave configuration entirely continuous for naturally flowing the cooling air. A configuration having a circumferential groove-shaped center-dented section steeply sunk on a part parallel to the axis line or a fringe-shaped configuration having upstream side or downstream side thereof radially extending toward the outside is not included in the present invention.
Specifically, when the steep sunk section exists, the flow of the cooling air often does not go smooth on the upstream and downstream side of the rotation locus. When only the upstream side extends, the cooling air is not likely to flow naturally at the downstream side, thus unable to conduct smooth discharge. When only the downstream side extends, backflow of the cooling air is likely on the upstream side, so that the cooling air is difficult to be smoothly sucked in.
In the present invention, a fan shroud may preferably be provided spaced apart from the rotation locus of the proximal end of the fan by a predetermined gap, the gap being constant on substantially the entire area between the rotation locus and the fan shroud.
According to the above arrangement, since the gap between the rotation locus and the fan shroud is constant, the inner circumference of the fan shroud is formed in a shape corresponding to the flow of the cooling air, i.e. bell-mouth shape, so that the gap is uniformly narrowed on the entire area. Accordingly, the tip clearance between the fan and the fan shroud can be narrowed on the suction and discharge side of the cooling air, thus decreasing swirl. Further, since the outer diameter of the fan on the inlet side and the discharge side can be enlarged, workload of the fan can be increased, thus further increasing static pressure and the wind flow of the fan.
In the present invention, an outer diameter of the fan on a side of a body to be cooled may preferably be smaller than a minimum inner diameter of the fan shroud.
When the outer diameter of the fan on a side of the object to be cooled is greater than the minimum inner diameter of the fan shroud, the fan cannot be accommodated in the fan shroud after the fan shroud is fixed to a predetermined position. Accordingly, in such case, the fan shroud is arranged in a divisible type composed of a plurality of small components and the respective small components are attached in a frame-shape around the fan after the fan is disposed adjacent to the object to be cooled, so that working process can be limited and much work is required for attaching the respective components. Especially, when the fan device is applied to the cooling system of the engine, the attachment work of the small components has to be conducted by putting a hand in a narrow engine room, thus complicating work process.
On the other hand, since the outer diameter of the fan on the side of the object to be cooled is smaller than the minimum inner diameter of the fan shroud, the fan can be easily accommodated in the fan shroud even after the fan shroud is assembled in the frame-shape, so that the work process can be flexibly changed in accordance with install position of the fan device, thus improving workability.
In the present invention, at least a part of an inner circumference of the fan shroud may preferably be formed of a porous noise absorbing material opposing to the rotation locus.
According to the above arrangement, jet noise caused by swirl between the proximal end of the fan and the fan shroud can be absorbed on account of sound absorption ability of the porous noise absorbing material attached to the fan shroud, thus remarkably reducing the noise.